A parking brake system of a car is used to keep the car motionless when it is parked. The traditional parking brake system is hand-operated and is commonly referred to as the “handbrake”. When starting a car equipped with a handbrake on a slope, the driver needs to manually release the handbrake in coordination with the accelerator and clutch (if used). The smooth use of the handbrake in such circumstances requires skill by the driver.
With the development of technology, electric parking brake (EPB) systems have been gradually replacing the traditional mechanical handbrake systems and becoming an important functional component of the car. The EPB system is capable of automatically activating four-wheel braking to prevent the car from rolling when the car is waiting for a green light, the car is parked, the car accidently stalls, or the car key is turned off. When it is desired to move the car from the stationary state, the parking brake is released simply by slightly pressing the accelerator pedal.
The EPB system includes an actuator having a motor driving an output shaft through a speed reduction mechanism. However, the conventional actuator requires tight tolerance component fabrication and is difficult to assemble. Therefore, the conventional actuator has low assembly precision and low operation smoothness and thus can be damaged easily.